One of the engine's more inter-
esting features has nothing to do
with emissions, NVH or power
output. A "Jake," or exhaust,
brake can be engaged to slow the
vehicle and reduce brake wear.
Unlike the version found on semi-
trucks, this unit is quiet and has
none of the loud reverberation
that typifes an over-the-road
system, though it works in the
same way. As an unthrottled
engine, a diesel always sends
a full air charge into the
cylinders where it is compressed
and returns this energy to the
crankshaft. By opening the
exhaust valves on deceleration,
the compression brake releases
the pressure in the cylinders, and
energy is absorbed. With cruise
control engaged it can be used
to maintain the desired speed in
downhill runs without applying
the brakes. When cruise control
is not in use, it adds braking
force to maintain vehicle control
regardless of vehicle load or
road grade. In either case, it
works seamlessly with the truck's
standard integrated trailer brake
controller.
When I spoke with Yackley, EPA
mileage ratings hadn't been
released, but it seems as though
35 mpg for the two-wheel drive
versions of the truck is not out of
the question. The towing capacity
is something that was established:
Two-wheel drive trucks are capable
of towing 7,700 lb or carrying
1,506 lb. of payload, while four-
wheel drive versions can handle
7,600 and 1,470 lb., respectively.
autofeldguide.com
AD&P; > December 2015 > FEATURE > Diminutive Duramax Diesel > Christopher A. Sawyer
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